POWER PLANT:-GUIDELINES

POWER PLANT

GUIDELINES

The following minimum conceptual requirements shall be applied to the machines and installations in a way to ease the maintenance tasks as far as possible:

 Gas Turbines. 

Through the instruction manuals related to the maintenance schedule of the gas turbines, the Contractor is required to carefully stipulate the scope and the frequency of the major inspections and overhauls, particularly as regards the hot gas path components.

 In addition, the following shall be included:

Bypass Damper,

 HRSG and Air Cooled Condenser

Adequate spacing in between the HRSG tube bundles, for tube replacement, off-load water washing of and on-load soot blowing system with retractable soot blowers to be provided.  0% Gas leakage on damper diverter is required to ensure safe maintenance on HRSGs.  Provisions for water washing air-cooled condensers ere are required.

  Accessibility

a]         All equipment/components shall be arranged / installed in such a way that each shall be easily and safely accessible for operation and maintenance. Permanent platforms shall be provided for all the equipment/instruments/valves etc. required to be visited during normal operation or maintenance.

 The access to the platform shall be through stairs wherever possible. Ladders shall only be provided where space or passage obstruction prohibits the provision of stairs, with Company / Engineer approval.

b]         The equipment to be visited during long-term maintenance (like six-monthly or annual maintenance etc) temporary accessibility arrangement shall be provided through A-frame ladders, extendable telescopic ladders, mobile platforms, scaffolding, etc.

 The type number and size shall be as per site requirements with Company/Engineer’s approval. At least eight (8) sets of scaffoldings 6 m high each, with lockable wheels and other accessories shall be provided for the plant.

c]         Special means shall be provided such as sky lifts etc. to reach the high elevation or ceiling mounted equipment like lighting, fire detectors, etc.

d]         All the outdoor/indoor equipment shall be reachable by suitable vehicles such as trucks, vacuum trucks, fork lifters, cranes etc. as applicable.

e]         The hoses or pipes provided with temporary pumps, vacuum trucks etc. shall be sufficient to reach the farthest equipment required to be served.

f]          All the indoor equipment must be reachable by crane. If not, electric hoisting/lifting with electric travelling facilities shall be provided with a travelling beam up to the point where removal by mobile means is possible.

g]         Manual hoists with travelling trolleys can be provided where approved by the Company/Engineer. Size, type, the quantity shall be as per Company/Engineer’s approval.

h]         The outdoor equipment shall be reachable by a mobile crane. If not, special arrangements shall be made to facilitate maintenance/dismantling and removal of such equipment with Company/Engineer’s approval.

i]          All building roofs having any equipment shall be accessible through stairs. For the low bay roof, three access stairs shall be provided, one at the centre and one (1) each at the end of the blocks. Crossover bridges shall be provided on a low bay roof, if required, to ensure that every piece of equipment is easily accessible.

j]          In hazardous areas, access shall be provided on at least two far apart locations to facilitate the emergency exit.

k]         Crossover platform shall be provided, wherever required.

l]          Four (4) low bed hand trolleys shall be provided for replacement of FM 200 cylinders.

m]        In the turbine hall, a 4-meter wide passage shall be provided throughout the length for access of vehicles, cranes, etc.

a]         In general, adequate space shall be provided for maintenance of equipment. The Contractor shall take into account the provision of adequate space for dismantling/removal of equipment such as draw out of the tube bundles, breakers, removal of turbine/generator rotors, HVAC equipment, etc.

b]         Electrical panels, cabinets, etc. shall have sufficient space around for the full opening of doors, maintenance, and removal if required.

c]         The arrangement of equipment shall be such that sufficient space is available during maintenance for the laydown of parts. The turbine hall arrangement should be on the basis of all the gas turbines of one block under maintenance simultaneously. The Contractor shall submit a scaled laydown drawing to demonstrate the availability of sufficient space and scheme for laydown of components of all gas turbines together.

d]         The arrangement of strainers shall be such that strainer baskets/elements, especially the Y-strainers close to the ground can be easily removed/replaced.

e]         The equipment shall have adequate headroom to facilitate lifting and removal, taking into account the space required for slings and hooks of lifting equipment.

Sufficient number of utility stations for service water and air shall be provided all over the plant for the cleaning operation during normal running as well as overhauling/maintenance of the equipment/component.

 Each utility station shall have a quick connection couplings, 25 m long air and water hoses with compatible couplings, on one-end and gun type nozzles on the other end mounted on a suitable stand.

 Number and location of utility stations shall be subject to Company/Engineer’s approval.

Maintenance Space

 -   Air/Water Utility Station

 -   Future Connections

In order to make the outages of running units to a minimum at the time of tie-in, all the future connections shall be provided with a valve and blind flange.

  Redundancy

a]         All essential equipment shall be redundant, bypasses shall be provided to facilitate maintenance of equipment, valves etc. without shutdown of main equipment and to prevent a single cause failure.
 b]         All the pumps, compressors shall be 2 x 110% or 3 x 60% to meet the redundancy requirements unless otherwise stated.
c]         All filters shall be duplex type unless otherwise stated.

 -   Valves

a]         All control valves shall have bypasses with isolation valves unless otherwise stated or the requirement is specifically waived by the Company/Engineer upon specific request and satisfactory acceptable technical justification by the Contractor.

b]         All motorized or pneumatic valves shall have the facility for manual operation also.

c]         Local operation facility shall be provided for all remotely operated valves to facilitate maintenance through open/close buttons and lockable/remote selector switch.

d]         Facility shall be provided for online stroking of all remote operated and control valves.

e]         Lockable valves shall be provided wherever required.

f]          The important motorized valves, which can shut down the unit if out of service, shall have bypass valves with isolation valves.

g]         The motorized valves/pneumatic valves on fuel lines shall have isolation valves upstream/downstream unless otherwise stated or approved by the Company/Engineer.

h]         The safety/relief valves, having common discharge lines shall be provided with lockable isolation valves upstream of the safety valve.

i]          Critical loop actuators such as ESD, EIV etc. shall be redundant with an online maintenance facility on the failed actuators.

  Piping and Valve Lists

a]         The Contractor shall submit a comprehensive pipe list covering the whole plant containing service, identification number, piping size, material, class/pressure rating or schedule number; design/operating pressure and temperature etc. The list shall also indicate the electrode used for welded pipes and the type/rating of gasket used in flanged pipes.

b]         A comprehensive valve list shall be submitted covering the whole plant, indicating valve identification number, type, service, pressure and temperature rating, material, make, operating pressure, temperature, type of electrode or type/rating of gaskets used in the connection of these valves etc.

c]         Three copies of these lists shall be submitted inbound form with two soft copies for use in future maintenance, repair, replacement etc.

 - Standardization of Equipment:

a]         As far as possible, the equipment shall be standardized throughout the plant to facilitate maintenance, less spare inventory requirements, ease in training etc. In particular, the following should be standardized as a minimum:

i.          HVAC equipment i.e. air handling units, fans, heaters, ventilation units, autonomous units, etc.            

ii.          Valves: as far as possible, the approved vendors shall be used for valves supply. In general, no more than five (5) vendors shall be used for the plant.

iii.         Pumps: as far as possible, shall be standardized along with their components like mechanical seals, etc.

iv.         Motors: as far as possible shall be standardized.

v.         Valve actuators: as far as possible, actuators shall be standardized.

vi.         Instruments: pressure, temperature & level gauges, transmitters, flow indicators/ gauges and transmitters, switches, totalizers, recorders etc. shall be standardized.

vii.        Electrical relays, breakers, switchgear: as far as possible shall be standardized.

viii.       Use of gateways/interface with DCS shall be minimized.

b]         Departure from standardization is possible with the approval of the Company/Engineer in special cases.

       Adequate lighting shall be provided for all indoor and outdoor equipment.  All the local instruments shall be readable at night. All the platforms stairs, passageways shall have adequate lighting.

       In general, no area of the plant has any equipment, valve, instruments, etc. shall be under darkness during the night.

      All the road crossings shall be provided with lights.

      The lux levels of different areas shall be as specified or if not specified shall be as approved by the Company/Engineer.

          Safety Provisions'

 a]         Provisions shall be made for safety during operation and maintenance. Particular care shall be taken for the following:  

i.          All the platforms shall have railing with toe plates.

ii.          The roofs having any equipment, valves, instruments or fittings shall have railing or parapet wall with stair(s) for access.

iii.         All the ladders, higher than 2.5 m shall be provided with safety cages.

iv.         All elevated equipment shall be provided with platforms, railing, stairs or ladders (as approved for safe maintenance).

v.         All openings such as ladders connection to platforms shall be provided with removable barriers.

vi.         Railings/walls, barriers etc. shall be provided around all the pits.

vii.        Any other safety requirement not explicitly specified in the specifications, but considered necessary by the Company/Engineer shall be provided by the Contractor at no extra cost or time consideration.

viii.       Crossover platforms shall be provided over pipes as per approval of the Company/Engineer.  The platform shall in general be provided to keep the shortest pedestrian route to and from any building or facility.

        The Contractor shall develop and submit a detailed list of lubricants used for various equipment/parts of the plant.

        The list shall include the name of the manufacturer of the lubricant used, equivalent lubricant for each type used from other manufacturers and:

i.          Quantity of lubricants used per charge.

ii.          Total quantity of each type of lubricant used in order to assess the annual requirement.

iii.         Time interval to replace the lubricant.

iv.         Viscosity & other characteristics such as viscosity index, flash point, pour point, etc.

Proper connection with valves and pipings shall be provided at easily accessible locations for the collection of samples.  If required due to space constraints, at the end of the sample collection, a hard pipe or a flexible pipe shall be provided to make the collection of samples easier.

a]         All protection relays shall be provided with test sockets to enable secondary injection tests using a comprehensive test bench for the following equipment:
i.          Generators,
ii.          Medium Voltage equipment
iii.         LV equipment

b]         Similarly, the facilities shall be provided for the injection of primary currents for all protection relays by use of primary current injection test set.

c]         All facilities shall be provided for safe maintenance and, interalia, sufficient earthing switches having a padlock facility or combined earthing breakers.

d]         All microprocessor-based control & monitoring systems and smart devices/instruments shall be fault-tolerant and equipped with self-diagnostic facilities.

e]         Test benches and kits shall be used for the calibration and checks of the thermo-couples (other TCs than the one of the gas turbines inlet temperature) and vibration pick-ups.